SEMICONDUCTOR DEVICES AND APPLICATIONS
The semiconductor device i.e., solid state device is capable of amplifying the weak signal. The devices are solid rather than hollow like the vaccum tube. These semiconductor devices are smaller in size, more rugged and less power consumption than vaccum tubes. The various semiconductor devices include semiconductor diode, Zener diode, transistor, JFET, MOSFET, UJT, SCR, DIAC and TRIAC etc. The semiconductor devices have very wide range of applications in various fields such as communication systems, medical electronics, microprocessor based systems, instrumentation, process control, aerospace, consumer electronics, etc.
The electrons present in the outer most orbit that are loosely bound to the nucleus are called valence electrons.
When an electric field is applied, the valence electrons get detached themselves from the nucleus, constituting the flow of current. These electrons are called conduction electrons.
The (range of) energy possessed by the electrons in an atom is called energy band.
The (range of) energy possessed by the conduction electrons is called conduction band.
The (range of) energy possessed by the valence electrons is called valence band.
Forbidden energy gap
The gap between the valence band and the conduction band is called forbidden energy gap.